This repo showcases Svelte VSCode extension port to VSCode web
If you don't know what Svelte is - go here
To enter github.dev mode - go here (or just press . in Github) you would then asked to install the recommanded asafamr.svelte-web extension - if not, install it manually.
Then, open a Svelte component. You should have most langague tool features in browser - autocompletion, syntax highlighting, full typescript support etc...